The present invention relates to a tandem pump unit used for various purposes.
More particularly, a first aspect of the present invention relates to a tandem pump unit with first and second hydraulic pumps, which respectively cooperate with first and second actuators driven through a hydraulic effect.
A hydraulic pump is used in various applications and in particular as the hydraulic pump adapted for operation in association with an actuator driven through the hydraulic effect. The description will hereinafter be made for the tandem pump unit by taking for example the case where it cooperates with first and second hydraulic motors serving as the actuators that respectively drive the right and left drive wheels.
For example, U.S. Pat. No. 4,920,733 discloses a vehicle including first and second hydraulic pumps respectively connected via first and second hydraulic lines to the first and second hydraulic motors for driving the right and left drive wheels. In this vehicle, the first and second hydraulic motors respectively have outputs variable in response to the adjustment of the input/output flow rates of the first and second hydraulic pumps, thereby controlling the rotational speed and rotational direction of the right and left drive wheels.
The vehicle disclosed in the above cited U.S. Pat. No. 4,920,733 has the first hydraulic pump and the second hydraulic pump separately arranged from one another, the former being operated in association with the first hydraulic motor, and the latter being operated in association with the second hydraulic motor. These separate hydraulic pumps pose various problems, such as troublesome mounting operation of the first and second hydraulic pump, troublesome conduit setting work between the pumps and the motors, and requiring separate housings which respectively accommodate the first and second hydraulic pumps.
The first aspect of the present invention has been therefor conceived in consideration of the prior arts. It is an object of the first aspect of the present invention to provide a tandem pump unit with first and second pumps connected to each other in series, while being connected to actuators via first and second hydraulic lines respectively, and is capable of lowering the manufacturing cost through the simplification of mounting operation and the reduction of the number of parts.
The second aspect of the present invention relates to a tandem pump unit with first and second hydraulic pumps, which respectively cooperate with first and second actuators driven through a hydraulic effect.
A hydraulic pump is used in various applications and in particular as the hydraulic pump adapted for operation in association with an actuator driven through the hydraulic effect. The description will hereinafter be made for the tandem pump unit by taking for example the case where it cooperate with first and second hydraulic motors serving as the actuators that respectively drive the right and left drive wheels.
For example, U.S. Pat. No. 4,920,733 discloses a vehicle including first and second hydraulic pumps respectively connected via first and second hydraulic lines to the first and second hydraulic motors for driving the right and left drive wheels. In this vehicle, the first and second hydraulic motors respectively have outputs variable in response to the adjustment of the input/output flow rates of the first and second hydraulic pumps, thereby controlling the rotational speed and rotational direction of the right and left drive wheels.
The vehicle disclosed in the above cited U.S. patent has the first hydraulic pump and the second hydraulic pump separately arranged from one another, the former being operated in association with the first hydraulic motor, and the latter being operated in association with the second hydraulic motor. These separate hydraulic pumps invite a complicated structure of the feeding passage for charging working hydraulic fluid to the pair of the first and second hydraulic lines, and pose various other problems.
A third aspect of the present invention relates to a pump unit with first and second hydraulic pumps that are respectively connected via first and second hydraulic lines to first and second actuators driven through a hydraulic effect.
A hydraulic pump is used in various applications and in particular as the hydraulic pump adapted for operation in association with an actuator driven through the hydraulic effect. The description will hereinafter be made for the pump unit by taking for example the case where it includes the first and second hydraulic motors serving as the actuators that respectively drive the right and left drive wheels.
For example, U.S. Pat. No. 4,920,733 discloses a vehicle including first and second hydraulic pumps respectively connected via first and second hydraulic lines to the first and second hydraulic motors for driving the right and left drive wheels. In this vehicle, the first and second hydraulic motors respectively have outputs variable in response to the adjustment of the input/output flow rates of the first and second hydraulic pumps, thereby controlling the rotational speed and rotational direction of the right and left drive wheels.
The vehicle disclosed in the above cited U.S. patent has the first hydraulic pump and the second hydraulic pump separately arranged from one another, the former being operated in association with the first hydraulic motor, and the latter being operated in association with the second hydraulic motor. Such a separate arrangement of the hydraulic pumps invites a complicated structure of a feeding passage for feeding working hydraulic fluid from a reservoir tank to the first hydraulic line and the second hydraulic line, and poses various other problems.
The third aspect of the present invention has been therefor conceived in consideration of the above prior art. It is an object of the third aspect of the present invention to provide a pump unit with the first and second hydraulic pumps that are respectively connected via the first and second hydraulic lines to the first and second actuators driven through the hydraulic effect, and that is capable of achieving a simplified structure of the feeding passage for feeding working hydraulic fluid to the hydraulic lines extending between the actuators and the hydraulic pumps.
A fourth aspect of the present invention relates to a pump unit with first and second hydraulic pumps that are respectively connected via first and second hydraulic lines to first and second actuators driven through a hydraulic effect.
A hydraulic pump is used in various applications and in particular as the hydraulic pump adapted for operation in association with an actuator driven through the hydraulic effect. The description will hereinafter be made for the pump unit by taking for example the case where it includes the first and second hydraulic motors serving as the actuators that respectively drive the right and left drive wheels.
For example, U.S. Pat. No. 4,920,733 discloses a vehicle including first and second hydraulic pumps respectively connected via first and second hydraulic lines to the first and second hydraulic motors for driving the right and left drive wheels. In this vehicle, the first and second hydraulic motors respectively have outputs variable in response to the adjustment of the input/output flow rates of the first and second hydraulic pumps, thereby controlling the rotational speed and rotational direction of the right and left drive wheels.
The vehicle disclosed in the above cited US patent has the first hydraulic pump and the second hydraulic pump separately arranged from one another, the former being operated in association with the first hydraulic motor, and the latter being operated in association with the second hydraulic motor. Such a separate arrangement of the hydraulic pumps invites a complicated structure of a feeding passage for feeding working hydraulic fluid for an HST (hydrostatic transmission) from a hydraulic fluid tank to the first hydraulic line and the second hydraulic line, and poses various other problems.
As a further disadvantage, the working hydraulic fluid between the hydraulic pumps and the actuators may increase in temperature due to the load from the outside. Such an increase in temperature of the working hydraulic fluid may invite various problems such as lowering of the volumetric efficiency, or lowering of the axle revolution speed if the hydraulic motors are used as the actuators for driving the drive wheels of the vehicle, deteriorating of the durability. However, the above-cited US patent does not teach any solutions to limit the temperature of the working hydraulic fluid of the HST.
The fourth aspect of the present invention has been therefor conceived in consideration of the above prior art. It is an object of the fourth aspect of the present invention to provide a pump unit with the first and second hydraulic pumps that are respectively connected via the first and second hydraulic lines to the first and second actuators driven through the hydraulic effect, and that is capable of effectively limiting the increase in temperature of the working hydraulic fluid to be replenished to the hydraulic lines between the actuators and the hydraulic pumps.
According to the first aspect of the present invention, there is provided a tandem pump unit that includes: a first hydraulic pump and a second hydraulic pump respectively having a first pump shaft and a second pump shaft respectively having adjacent ends connected together so that the first and second pump shafts are coaxially aligned and non-rotatably connected in tandem; a common housing for accommodating the first hydraulic pump and the second hydraulic pump; and a first center section and a second center section that respectively support the first and second hydraulic pumps.
The tandem pump unit of the above arrangement can reduce the number of the parts and hence the manufacturing cost, in comparison with a conventional tandem pump unit, which requires a separate housing for each pump unit. As an additional advantage, the tandem pump unit allows both the first and second hydraulic pumps to be mounted in position only by mounting the common housing with the first and second hydraulic pumps therein. Whereby, the efficiency in assembling operation can be enhanced.
Furthermore, the common housing has first and second openings respectively formed at opposed ends of the housing with respect to the pump shaft direction, and a bearing wall located midway between the first and second openings. The first and second openings allow the first and second hydraulic pumps to pass therethrough, and the bearing wall supports the connection portions of the first and second pump shafts. The first and second openings are adapted to be respectively sealed by the first and second center sections respectively supporting the first and second hydraulic pumps.
Therefore, the first and second hydraulic pumps can be respectively placed through the first and second openings into the housing with the first and second hydraulic pumps being respectively supported by the first and second center sections. Thus, the assembling efficiency of the tandem pump unit can be enhanced. In addition, either one or both of the pumps can easily be removed from the housing, while the housing is still mounted on an object such as a vehicle, thereby achieving an improved operation efficiency in maintenance work, or the like.
Furthermore, the tandem pump unit of the first aspect of this invention is designed so that the first and second center sections are disposed at the opposed ends of the housing with respect to the pump shaft direction in the housing excluding the portion between the first and second hydraulic pumps, thereby allowing for great flexibility in designing the adjacent ends of the first and second pump shafts to be connected together.
The tandem pump unit of the first aspect of this invention preferably includes a coupler for non-rotatably receiving the adjacent ends of the first and second pump shafts.
Preferably, the coupler is rotatably supported in a bearing hole formed in the bearing wall via a bearing member.
In the case where the first and second hydraulic pumps are axial piston pumps of a variable displacement type respectively having first and second angularly adjustable swash plates of cradle type, the bearing wall is preferably designed to have a side facing the first and second hydraulic pumps that forms guiding surfaces for slidingly guiding spherical convex surfaces formed in rear sides of the swash plates, which rear sides are opposed to surfaces facing the first and second hydraulic pumps.
According to the second aspect of the present invention, there is provided a tandem pump unit that includes the integral arrangement of a first hydraulic pump and a second hydraulic pump. The first hydraulic pump with a first pump shaft is adapted to be connected to a first actuator via a first pair of hydraulic lines. The second hydraulic pump with a second pump shaft is adapted to be connected to a second actuator via a second pair of hydraulic lines. The first pump shaft and the second pump shaft respectively have adjacent ends connected together so that the first and second pump shafts are coaxially aligned and non-rotatably connected in tandem. The tandem pump unit of the second aspect of the present invention further includes a charge line disposed within the tandem pump unit and having a first end communicating with either a reservoir or a hydraulic fluid feeding mechanism and a second end adapted to communicate with the first pair of hydraulic lines and the second pair of hydraulic lines, respectively.
The tandem pump unit of the above arrangement allows hydraulic fluid to be replenished into the first pair of hydraulic lines and the second pair of hydraulic lines, only by connecting a hydraulic fluid feeding mechanism such as a charge pump to the first opening of the charging line. Whereby, the piping structure for charging can be simplified, and the manufacturing cost can be lowered through the reduction of the number of parts and the improved efficiency in assembling operation. Also, the workability in maintenance can be improved.
As an additional advantage, the charge line disposed within the pump unit is unlikely to be damaged by the contact against external parts, thereby effectively preventing the leakage of the hydraulic fluid to the outsides from the charge line. This hydraulic fluid leakage preventive arrangement is advantageous particularly when the pump unit is used in vehicles for traveling on lawns or other grounds such as a riding mower, a walk behind mower, a commercial ride-on mid-mount-deck lawnmower, a tractor, or other device.
In one case, the tandem pump unit of the second aspect has preferably a common center section having oppositely facing sides with respect to the pump shaft direction, respectively supporting the first and second hydraulic pumps via the oppositely facing sides, and a first pump housing and a second pump housing for respectively accommodating the first hydraulic pump and the second hydraulic pump. The common center section forms a first pair of inlet/outlet ports and a second pair of inlet/outlet ports. The first pair of inlet/outlet ports respectively serve as connection ports for connection with the first pair of hydraulic lines and the second pair of inlet/outlet ports respectively serve as connection ports for connection with the second pair of hydraulic lines. The charge line has a first bore portion, a conduit and a second bore portion. The first bore portion is formed in a peripheral wall of either the first pump housing or the second pump housing with a first end opening to the outside of the either the first pump housing or the second pump housing so as to communicate with the either the reservoir or the hydraulic fluid feeding mechanism and a second end opening to the inside of the either the first pump housing or the second pump housing. The conduit is disposed within the either the first pump housing or the second pump housing with a first end connected to the second end of the first bore portion and a second end extending to the common center section. The second bore portion is formed in the common center section with a first end connected to the second end of the conduit and a second end communicating with the first pair of inlet/outlet ports and the second pair of inlet/outlet ports, respectively.
In another case, the tandem pump unit of the second aspect also includes a common center section having oppositely facing sides with respect to the pump shaft direction, respectively supporting the first and second hydraulic pumps via the oppositely facing sides, a first pump housing and a second pump housing for respectively accommodating the first hydraulic pump and the second hydraulic pump. The common center section forms a first pair of inlet/outlet ports and a second pair of inlet/outlet ports. The first pair of inlet/outlet ports respectively serve as connection ports for connection with the first pair of hydraulic lines, and the second pair of inlet/outlet ports respectively serve connection ports for connection with the second pair of hydraulic lines. The charge line has a third bore portion and a fourth bore portion. The third bore portion is formed in a peripheral wall of either the first pump housing or the second pump housing with a first end opening to the outside of the either the first pump housing or the second pump housing so as to communicate with the either the reservoir or the hydraulic fluid feeding mechanism and a second end extending to the common center section. The fourth bore portion is formed in the common center section with a first end connected to the second end of the third bore portion and a second end communicating with the first pair of inlet/outlet ports and the second pair of inlet/outlet ports, respectively.
Preferably, the common center section forms a hydraulic fluid communication hole for communication between the first and second pump housings.
In still another case, the tandem pump unit of the second aspect of the present invention also includes a common pump housing for accommodating the first and second hydraulic pumps, a first center section and a second center section for respectively supporting the first hydraulic pump and the second hydraulic pump. The common pump housing has a first opening and a second opening respectively formed at opposed ends of the pump housing with respect to the pump shaft direction. The first and second openings allow the first and second hydraulic pumps to pass therethrough. The first and second center sections are respectively connected to the common pump housing so as to seal the first and second openings in a liquid tight manner. The first and second center sections respectively form a first pair of inlet/outlet ports and a second pair of inlet/outlet ports serving as connection ports for connection respectively with the first pair of hydraulic lines and the second pair of hydraulic lines. The charge line has a first end opening to the outside of either the first center section or the second center section so as to communicate with the either the reservoir or the hydraulic fluid feeding mechanism, and a second end communicating with the first pair of inlet/outlet ports and the second pair of inlet/outlet ports, respectively.
Preferably, the common pump housing has a bearing wall located midway thereof with respect to the pump shaft direction to support the adjacent ends of the first and second pump shafts. The bearing wall divides the common pump housing into a first hydraulic pump accommodation chamber and a second hydraulic pump accommodation chamber for respectively accommodating the first hydraulic pump and the second hydraulic pump.
Preferably, the common pump housing is designed to allow hydraulic fluid to communicate between the first hydraulic pump accommodation chamber and the second hydraulic pump accommodation chamber.
According to the third aspect of the present invention, there is provided a tandem pump unit for operation in association with actuators. The tandem pump unit includes the integral arrangement of a first hydraulic pump and a second hydraulic pump. The first hydraulic pump with a first pump shaft is adapted to be connected to a first actuator via a first pair of hydraulic lines, and the second hydraulic pump with a second pump shaft is adapted to be connected to a second actuator via a second pair of hydraulic lines. The first and second pump shafts respectively have adjacent ends connected together so that the first and second pump shafts are coaxially aligned and non-rotatably connected in tandem. The tandem pump unit also includes a center section supporting the first hydraulic pump and the second hydraulic pump, a housing accommodating the first hydraulic pump and the second hydraulic pump, and a reservoir tank supportingly connected to the single unit for storing hydraulic fluid to be replenished to the first pair of hydraulic lines and the second pair of hydraulic lines. The first hydraulic pump, the second hydraulic pump, the center section and the housing are integrally connected together to constitute a single unit.
The pump unit of the above arrangement can improve an efficiency in mounting the first and second hydraulic pumps on an object such as a vehicle, and shorten the length of the piping for replenishing the hydraulic fluid from the reservoir tank to the first pair of hydraulic lines and the second pair of hydraulic lines, thereby lowering the manufacturing cost, and improving an efficiency in replenishing the hydraulic fluid through the decrease of the resistance force between the hydraulic fluid and the pipe wall, and producing other desirable effects
Preferably, the single unit of the tandem pump unit of the third aspect of the present invention is designed so that the housing can serve as a hydraulic fluid tank, and the pump unit further includes a hydraulic fluid communication passage for providing a free fluid communication between the reservoir tank and the housing. With this arrangement, the number of the pipes required between the first and second hydraulic pumps, and the first and second actuators can be reduced to substantially four pipes only, specifically the first pair of hydraulic lines and the second pair of hydraulic lines. Thus, as compared with the conventional arrangements, the pump unit of this arrangement can achieve a lower manufacturing cost, an improved assembling efficiency and an excellent workability in maintenance. Since the housing itself also serves as a hydraulic fluid tank, the reservoir tank can compactly be made.
The tandem pump unit of the third aspect of the present invention preferably has the following arrangement. Specifically, the center section forms a first pair of hydraulic passages respectively having first ends communicating with the first hydraulic pump and second ends opening to the outside of the center section to form connection ports for connection with the first pair of hydraulic lines, a second pair of hydraulic passages respectively having first ends communicating with the second hydraulic pump and second ends opening to the outside of the center section to form connection ports for connection with the second pair of hydraulic lines, and a charging passage having a first end opening to the outside of the center section to form an inlet port for charging, serving as an inlet for the hydraulic fluid to be replenished and a second end communicating with the first pair of hydraulic passages and the second pair of hydraulic passages via check valves. The charging passage is connected to a pressure relief line communicating with the housing via a relief vale, and the inlet port for charging is connected to the reservoir tank via a hydraulic fluid replenishing passage.
The tandem pump unit of the third aspect of the present invention also preferably has the following arrangement. Specifically, the tandem pump unit includes a cooling fan provided near the single unit. The cooling fan is adapted to be driven in synchronism with the first and second hydraulic pumps. The reservoir tank is connected to the single unit in such a manner as to form a clearance therebetween, into which a cooling air stream is drawn from the cooling fan. The hydraulic fluid communication passage and the hydraulic fluid replenishing passage are disposed in such a manner to traverse the clearance. The thus arranged pump unit can limit the temperature increase of the hydraulic fluid stored in the reservoir tank and the housing, and also effectively limit the temperature increase of the hydraulic fluid flowing through the hydraulic fluid replenishing passage and the hydraulic fluid communication passage, thereby improving the transmission efficiency between the hydraulic pumps and the actuators.
According to the fourth aspect of the present invention, there is provided a tandem pump unit that includes: a first hydraulic pump and a second hydraulic pump respectively having a first pump shaft and a second pump shaft that are coaxially aligned and non-ratably connected in tandem; a center section supporting the first hydraulic pump and the second hydraulic pump; and a housing accommodating the first hydraulic pump and the second hydraulic pump. The housing is adapted to be used as a hydraulic fluid tank. A hydraulic fluid circulation mechanism is also provided for taking the hydraulic fluid from the hydraulic tank, and again returning the same to the hydraulic tank. The hydraulic fluid circulation mechanism is designed to cool the hydraulic fluid while circulating the same.
The tandem pump unit of the above arrangement can effectively limit the increase in temperature of the hydraulic fluid stored within the hydraulic tank, thereby effectively preventing deterioration in working efficiency of a hydraulic actuation device.
Preferably, the circulation mechanism of the tandem pump unit of the fourth aspect of the present invention includes a circulation line, at least a portion of which serves as a conduit; the circulation line having a first end communicating with the inside of the hydraulic tank and a second end again communicating with the inside of the hydraulic tank. The conduit has at least a portion provided thereon with cooling fins.
Further, the pump unit of the fourth aspect of the present invention preferably has the following arrangement. The center section forms a first pair of hydraulic passages respectively having first ends communicating with the first hydraulic pump and second ends opening to the outside of the center section to form connection ports for connection with the first pair of hydraulic lines, a second pair of hydraulic passages respectively having first ends communicating with the second hydraulic pump and second ends opening to the outside of the center section to form connection ports for connection with the second pair of hydraulic lines, and a charging passage having a first end communicating with the hydraulic fluid tank to form an inlet port for charging, serving as an inlet for the hydraulic fluid to be replenished and a second end communicating with the first pair of hydraulic passages and the second pair of hydraulic passages via check valves. The tandem pump unit further includes: a charge pump for sucking the hydraulic fluid stored within the hydraulic fluid tank and then discharging the same into the inlet port for charging; and a pressure relief line having a first end connected to the charging passage via a relief valve and a second end forming a drain port through which the hydraulic fluid from the relief valve is drained. The second end of the pressure relief line is connected to the conduit, and the charge pump constitutes a part of the hydraulic fluid circulation mechanism.
Preferably, the pump unit of the fourth aspect of the present invention further includes a reservoir tank, in which the reservoir tank is in free fluid communication with the housing via a hydraulic fluid communication passage, and forms a hydraulic fluid tank in cooperation with the housing, and the inlet port for charging communicates with the reservoir tank via a hydraulic fluid replenishing passage.
Preferably the pump unit of the fourth aspect of the present invention further includes cooling fins provided on the hydraulic fluid replenishing passage and the hydraulic fluid communication passage.
Further, the pump unit of the fourth aspect of the present invention preferably has the following arrangement. Specifically, a cooling fan adapted to be driven in synchronism with the first and second hydraulic pumps is provided near the housing. The reservoir tank is connected to the housing in such a manner as to form a clearance therebetween, into which a cooling air stream from the cooling fan is drawn. The hydraulic fluid communication passage and the hydraulic fluid replenishing passage are disposed to transverse the clearance.
A cooling air duct is preferably provided in the pump unit of the fourth aspect of the present invention, so that a cooling air stream from the cooling fan is drawn into the clearance along the cooling air duct.